Vehicle water pumps include a shaft driven impeller, which is often formed of stamped steel and friction fitted to the end of a steel drive shaft. Impellers have also been molded of plastic, which has the obvious advantages of non corrosion and light weight, but it is not practical to also form the impeller drive shaft of plastic. Consequently, the shaft and impeller cannot be formed as one unit, and the impeller must somehow be joined securely and non-turnably to the shaft. One known connection is disclosed in U.S. Pat. No. 4,155,333 to Maggiorana, which shows matching non circular surfaces on the shaft and impeller to prevent relative turning, and a nut and washer connection to secure the impeller to the shaft. A more complex connection between plastic impeller and steel shaft is disclosed in U.S. Pat. No. 4,363,603 to Peterson. A threaded plug on the end of the shaft is screwed into a threaded metal insert molded into the center of the impeller. A sleeve of the impeller with a cutout on the edge slip fits over a knurled outer surface formed on the shaft. A knurled segment that interfits with the knurled shaft surface also fits closely into the impeller sleeve cutout to lock the impeller to the shaft and prevent relative turning. A separate collar is used to hold the locking segment into the cutout and onto the shaft. Clearly, this represents a quite complex and potentially expensive connection, since it requires the molding of the insert into the impeller, as well as the separate locking segment and collar.